Composition of matter



Patented @ct. d, 1931 GREGORY J. COMSTOCK, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO FIRTH-STER- LING STEEL COMPANY, OF MCKEESPORT, PENNSYLVANIA, A

SYLVANIA.

CORPORATION OE PENN COMPOSITION OF MATTER No Drawing.

It has heretofore been proposed in the art, to form compositions of matter from an abrasive material and a suitable binding agent. For this purpose tungsten carbide has been used with various metallic binders. While such a combination gives desirable results for use in many difi'erent ways, the compositions as heretofore produced have been comparatively expensive, thereby tending to to discourage their widest possible application.

In accordance with the present invent on there is provided an improved composltion of matter, as well as an improved method of manufacturing the same, based primarily on the use of easily obtained, relatively inexpensive materials, resultingtln a product having such relatively high efficiency as to permit of its satisfactory substitution, in many cases, for the more expensive materials heretofore so available.

This invention contemplates the production of a material suitable forthe formation of tools, such as bits, shapers, drills, cutters, saws, and the like, as well as dies for both drawing and extrusion pur oses. It also contemplates the production 0 dressing tools, metallic grinding stones and knife sharpeners and other similar devices and tools requiring high abrasive or cutting characterisso ties.

In carrying out the present invention, I utilize a cutting or abrading agent in combination with a suitable metallic binding agent serving to bond together the particles of the cutting agent. As a cutting agent I utilize silicon carbide or vitrified zirconium oxide, and as a metallic binder I utilize nickel, vanadium or iron. The preferred combina-\ tion comprises the use of silicon carbide as a cutting agent with nickel or iron as the binding agent, all of these difierent materials being readily obtainable at a relatively small cost.

While the properties of silicon carbide are as well recognized by those skilled in the art,

Application flied April 9, 1928. Serial No. 268,389.

the fullest advantages of these roperties have not heretofore been realized, ecause of limitations in the efiiciency of the binders previously utilized. l

I have found that desirable results may be accomplished by taking the desired uantity of silicon carbide or an equivalent a rasive, reducing the same to finely divided form' preferably such that it will pass through a two hundredmesh screen, and mixing the same with the desired amount of a" suitable metallic binding agent of the character herein referred to, which has been similarly finely divided. o

The cutting agent or agents and the binding agent having been reduced to the desired fineness, they are mixed together in varying proportions, depending upon the characteristics which are desired in the final composition. Where brittleness of the" product is no limiting factor, smaller percentages of binder may be used, but where strength and resistance to shock are required, larger percentages of binder must be present.

Itis notable that Where the binder is increased, the cutting or abrading value of the abrasive and likewise the cutting or abrading value of the product is necessarily decreased due to the relatively greater dispersion of the cutting particles. For example, in cases of the character first referred to I may utilize as high as 95% of the cutting agent or cutting agents with desirable results, while in the latter case the binding'agent may be increased up to 95% or even higher. I

In some cases it is desired to provide a composition of matter of such nature that it lends itself to shaping and deforming by hot workin In such cases I utilize not 5 less than thirty, and preferably not less than n 5 fifty, percent of the binding agent, although variat1ons in this amount may be made one way or the other while retaining some degree of workability.

Silicon carbide Nickel Example U As a specific example of a compositionof brittle character useful for the productron of dressing tools, metal grinding stones,'kn 1fe sharpeners, and the like, 1 refer to the tolllowing:

Silicon carbide 90% Nickel 10% Ewomple H] Where it is important that theresulting product have workable characteristics, 1 have found that a composition in accordance with the following, gives desirable results:

Silicon carbide Nickel 50% Having determined upon the proper composition depending upon he character wh ch the resulting roduct is to havefor its specific application, may proceed in accordance with any of four diiierent methods. The first of these involves the pressing to shape followed by fusing without any subsequent pres sure; the second involves the pressing to shape followed either in sequence or s1m ul-' taneously by heat and pressure; the third involves the application of heat and pressure simultaneously without any preliminary pressure; while the fourth involves the application of heat followed by the application of pressure, without any preliminary press- Tn accordance with the first method, which will hereinafter be referred to as the cold compacting method, 1 preferably form. a paste by using gum tragacanth 1n the amount of one ounce of the gum tragacanth to a pint of water, and add this paste to the mixture of cutting agent or cuttlng agents and binding agent in the ratio of about of 1% by weight. This mixture is then subjected to pressure while cold, the pressure preferably being of the order of 150 tons to the square inch.

This produces a closely compacted mixture which is then subjected to a temperature sulficiently high to melt the'bindi'ng agent and cause it to actually flow around the cutting agent or cutting agents, so that upon cooling, such agent or agents will be substantially uniformly dispersed or distributed throughout the product with each particle.

firmly bonded in the binding material, which in this case forms a metal matrix.

neaaeta lln the second method the preliminary steps of forming a paste-like mixture, and pressing the same are followed. Thereafter this mixture is subjected to heat to fuse the binding agent, and either simultaneously with the application of the heat, or subsequently thereto while the mixture is still hot, is subjected to pressure.

In the third method, the preliminary compactin is dispensed with, the mixture being su jected in a suitable mold to heat and pressure simultaneously.

In accordance with the fourth method, which also obviates the necessity for any preliminary cold pressing, the mixture is subjected to the desired temperature conditions, and thereafter, while still hot, is subjected to pressure.

The second, third and fourth methods have the advantage of providing pressure at such a time as to tend to close up any pores which may have formed under the heat treatment by reason of the volatilization of any of the ingredients. Also, these three last-mentioned processes require a materially lower pres.- sure, pressures as low as from to 150 pounds per square inch producing satisfactory results with some mixtures.

lln heating, in each of the methods above referred to, I prefer to employ temperatures in the neighborhood of 2800 F, although it will be obvious that this temperature depends on the particular metallic binder employed, and may vary within fairly wide limits. During the heating, suitable precaus tions must be taken to prevent oxidation of the product. This may be accomplished, for example, by heating in a reducing atmosphere of hydrogen.

In all cases where a paste has been formed by the use of gum tragacanth the application of heat volatilizes the same from the mixture.

The hardness of the composition in accordance with my invention is such that once 1t has been produced it does not lend itself to grinding or cutting by known methods. It is therefore desirable, in case the proportions are not such as to produce a wbrkable product, i. e., a product lending itself to shaping or deformation when heated to a suitable temperature, t o'subject the mixture to pressure in a mold of the desired configuration of the finished article. In this manner. a completed article, such as a tool, can be formed directly from the mixture.

While in the specific examples herein given I have referred to the use of silicon carbide, this being the present preferable cutting agent, either alone or in conjunction with other cutting agents of the character herein referred to, it will be understood that the other cuttingagents may be utilized to replace or part y replace the silicon carbide, the results obtained varying with the charlltl rename acteristics of the particular cutting agent utilized.

It is to be understood that the form of the invention described is the preferred embodiment and that the invention is not limited except as required by the appended claims, it being understood that the examples herein specified are given by way of illustration only and not by way of limitation.

I claim:

1. A sintered aggregate amenable to shapino while hot, comprising silicon carbide partic es embedded in a matrix of nickel, the nickel comprising at least 30% by weight of the aggregate.

2. A sintered aggregate amenable to shaping While hot, comprising silicon carbide particles embedded in a matrix of nickel, the silicon carbide and nickel being in about equal proportions by Weight.

3. A sintered a gregate comprising finely divided silicon car bide bonded in a matrix of nickel, the silicon carbide constituting from a major portion to about 95% of the aggregate.

4. A sintered aggregate comprising finely divided silicon carbide bonded in a matrix of nickel, the silicon carbide constituting from about to of the aggregate.

5. A sintered aggregate comprising finely divided silicon carbide bonded in a matrix of nickel, the silicon carbide constituting about 94% and the nickel about 6% of the aggregate.

In testimony whereof I have hereunto set my hand.

GREGORY J. COMSTOCK. 

